1. Field of the Invention
The present invention relates to data communication by a class-2 service.
2. Description of the Related Art
The communication sequence of the class-2 service is known as, e.g., an ITU-T (International Telecommunication Union-Telecommunication sector) recommendation T.32.
The class-2 service asynchronously executes data transfer from a data terminal equipment (to be referred to as DTE hereinafter) to a data circuit-terminating equipment (to be referred to as DCE hereinafter), and data transmission from the DCE to the circuit. That is, the class-2 service can end data transfer from the DTE to the DCE regardless of the execution status of data transmission from the DCE to the circuit.
The ITU-T recommendation T.32 stipulates that the DTE waits for a command from the DCE after the end of image data transfer to the DCE. The recommendation T.32 also stipulates that the DCE should send to the DTE a command representing the end of data transmission to the circuit after the DCE receives data transferred from the DTE.
Hence, the DTE must wait for a command from the DCE until the DCE ends data transmission to the circuit and sends a command representing the end of data transmission.